Ultrasonic flow sensor system including a flow tube with an absorber sheath encirling the flow tube

ABSTRACT

A flow sensor sub-assembly for sensing flow of a fluidic medicament includes a flow tube having a flow tube inlet and a flow tube outlet, and an acoustical transmission rate. The medicament flows through the flow tube. A first piezo element is arranged at an upstream position of the flow tube and a second piezo element is arranged at a downstream position of the flow tube, such that the first piezo element and the second piezo element are mounted apart a pre-selected distance from each other. An absorber sheath encircles the flow tube. The absorber sheath has an upstream end and a downstream end. The absorber sheath is comprised of a material with an acoustical transmission rate different than the flow tube.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/381,518, Apr. 11, 2019, which is a continuation of U.S. patent application Ser. No. 15/950,614, filed Apr. 11, 2018 (now U.S. Pat. No. 10,295,384), which is a continuation of U.S. patent application Ser. No. 15/247,120, filed Aug. 25, 2016 (now U.S. Pat. No. 9,970,794), which claims the benefit of U.S. Provisional Patent Application No. 62/211,309, filed Aug. 28, 2015, the disclosures of each of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Disclosure

The present disclosure relates generally to a flow sensor system. More particularly, the present disclosure relates to a flow sensor system for providing intravenous bolus injections of medication to a patient which provides healthcare professionals with an automated record of medication, concentration, volume, dose, and time of each injection. Preferably, the system has an ultrasonic flow sensor.

Description of the Related Art

There is a need to reduce medication error at bedside during bolus delivery. It would be advantageous to provide a record of, and electronically measure, bolus delivery which allows monitoring bolus delivery and automatic documentation of bolus delivery as part of a patient's health record. Additionally, it would be advantageous to provide alerts when bolus delivery inconsistent with a patient's medical record is about to occur.

SUMMARY OF THE INVENTION

The present disclosure provides a system for sensing a flow of a fluidic medicament. The system includes an intelligent injection port which may attach to an injection site (such as a “Y Site” or a stop cock) for manually administered IV injections. The system includes two main sub-assemblies: a single-use flow sensor and a reusable base unit, which fit together prior to use. The single-use flow sensor includes a flow tube sub-assembly.

In accordance with an embodiment of the present invention, a flow sensor sub-assembly for sensing flow of a fluidic medicament includes a flow tube having a flow tube inlet and a flow tube outlet, and an acoustical transmission rate. The medicament flows through the flow tube. The flow sensor sub-assembly also includes a first piezo element arranged at an upstream position of the flow tube and a second piezo element arranged at a downstream position of the flow tube, such that the first piezo element and the second piezo element are mounted apart a pre-selected distance from each other. The flow sensor sub-assembly also includes an absorber sheath encircling the flow tube, having an upstream end and a downstream end, and the absorber sheath includes a material with an acoustical transmission rate different than the flow tube.

In one configuration, the flow tube further includes end fittings adapted for securing the flow tube to the fittings and the first and second piezo elements are mounted to the end fittings. In another configuration, the upstream end and the downstream end of the absorber sheath are each spaced apart from the end fittings by a distance of about 6 mm.

In another configuration, the absorber sheath is heat shrunk onto the outside diameter of the flow tube. In yet another configuration, the absorber sheath is adhered to the flow tube with an adhesive. In one configuration, the adhesive is acoustically transparent.

In one configuration, the flow tube is a stainless steel material. In another configuration, the absorber sheath is a plastic material. In yet another configuration, the absorber sheath is a PVC material. In yet another configuration, the absorber sheath is an elastomeric material.

In one configuration, an attenuation of signal is improved by at least 50% over a flow sensor sub-assembly without the absorber. In another configuration, an attenuation of signal is improved by at least 60% over a flow sensor sub-assembly without the absorber.

In one configuration, the first piezo element and the second piezo element are annular in shape and encircle the flow tube at each respective mounting point.

In another configuration, the flow sensor sub-assembly is contained within a flow sensor housing, and the flow sensor housing is coupled to a flow sensor base which contains a microprocessor and a circuit for providing an electrical signal from the flow sensor sub-assembly to the microprocessor within the flow sensor base. In one configuration, the flow sensor sub-assembly is disposed after the flow sensor sub-assembly is used to sense the flow of at least one fluidic medicament. In another configuration, a flow sensor system includes the flow sensor sub-assembly and the flow sensor base, and the flow sensor base is used with a different flow sensor sub-assembly.

In accordance with another embodiment of the present invention, a flow sensor sub-assembly for sensing flow of a fluidic medicament includes a flow tube sub-assembly and a first piezo element arranged at an upstream position of the flow tube sub-assembly and a second piezo element arranged at a downstream position of the flow tube sub-assembly, such that the first piezo element and the second piezo element are mounted apart a pre-selected distance from each other. The flow tube sub-assembly has a first flow tube and a second flow tube each having a respective flow tube inlet and a respective flow tube outlet, and an outside diameter, and the medicament flows through the flow tubes. The flow tube sub-assembly also has an absorber sheath connecting the first flow tube outlet to the second flow tube inlet with a gap therebetween, and the medicament flows through at least a portion of the absorber sheath.

In one configuration, the flow tube sub-assembly further includes end fittings adapted for securing each flow tube to the end fittings and the first and second piezo elements are mounted to the end fittings.

In another configuration, the absorber sheath is heat shrunk onto at least a portion of the outside diameter of each of the flow tubes. In yet another configuration, the absorber sheath is adhered to at least a portion of each of the flow tubes with an adhesive.

In one configuration, the flow tube is a stainless steel material. In another configuration, the absorber sheath is a plastic material. In yet another configuration, the absorber sheath is a PVC material. In yet another configuration, the absorber sheath is an elastomeric material.

In one configuration, the first piezo element and the second piezo element are annular in shape and encircle the flow tube at each respective mounting point.

In one configuration, the flow sensor sub-assembly is contained within a flow sensor housing. The flow sensor housing is coupled to a flow sensor base which contains a microprocessor and a circuit for providing an electrical signal from the flow sensor sub-assembly to the microprocessor within the flow sensor base. In another configuration, the flow sensor sub-assembly is disposed after the flow sensor sub-assembly is used to sense the flow of at least one fluidic medicament. In yet another configuration, a flow sensor system includes the flow sensor sub-assembly and the flow sensor base, and the flow sensor base is used with a different flow sensor sub-assembly.

In one configuration, an attenuation of signal is improved by at least 60% over a flow sensor sub-assembly without the gap between the first flow tube and the second flow tube. In another configuration, an attenuation of signal is improved by at least 75% over a flow sensor sub-assembly without the gap between the first flow tube and the second flow tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following descriptions of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a distally-directed perspective view of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 2 is a proximally-directed perspective view of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 3A is a proximal elevation view of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 3B is a distal elevation view of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 4A is a side elevation view of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 4B is an enlarged detail view of a portion of FIG. 4A as illustrated by Detail A.

FIG. 5A is a perspective view of a base of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 5B is a perspective view of the base of FIG. 5A illustrating the optical and electrical components.

FIG. 6 is a perspective view of a flow sensor of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 7 is another perspective view of a flow sensor of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 8 is an exploded, perspective view of a flow sensor of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 9 is a perspective view of a flow sensor of a flow sensor system in accordance with an embodiment of the present invention.

FIG. 10A is a side elevation view of a syringe compatible with a flow sensor system in accordance with an embodiment of the present invention.

FIG. 10B is an enlarged detail view of a portion of FIG. 10A as illustrated by Detail B.

FIG. 10C is a side elevation view of a tip label for a syringe compatible with a flow sensor system in accordance with an embodiment of the present invention.

FIG. 11A is a perspective view of a charger for a flow sensor system in accordance with an embodiment of the present invention.

FIG. 11B is an enlarged detail view of a portion of FIG. 11A rotated at a clockwise angle as illustrated by Detail C.

FIG. 11C is a top elevation view of a charger for a flow sensor system in accordance with an embodiment of the present invention.

FIG. 11D is a cross-sectional view taken along line X-X of FIG. 11C, with a base of a flow sensor system received within a portion of the charger, in accordance with an embodiment of the present invention.

FIG. 12 is a perspective view of a flow sensor and a mount in accordance with an embodiment of the present invention.

FIG. 13 is a perspective view of a flow tube sub-assembly in accordance with an embodiment of the present invention.

FIG. 14A is a schematic representation of a computer display in an anesthesia view in accordance with an embodiment of the present invention.

FIG. 14B is a schematic representation of a computer display in a tabular view in accordance with an embodiment of the present invention.

FIG. 15 is a perspective view of an upstream portion of a flow tube sub-assembly in accordance with an embodiment of the present invention.

FIG. 16 is a perspective view of an upstream portion of a flow tube sub-assembly in accordance with an embodiment of the present invention.

FIG. 17 is a perspective view of an upstream portion of a flow tube sub-assembly in accordance with an embodiment of the present invention.

FIGS. 18A-D show a process for applying an absorber sheath and end fittings to a flow tube in accordance with an embodiment of the present invention.

FIGS. 19A-D show a process for applying an absorber sheath and end fittings to a flow tube in accordance with an embodiment of the present invention.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.

DETAILED DESCRIPTION

The following description is provided to enable those skilled in the art to make and use the described embodiments contemplated for carrying out the invention. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present invention.

For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations, except where expressly specified to the contrary. It is also to be understood that the specific devices illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the invention. Hence, specific dimensions and other physical characteristics related to the embodiments disclosed herein are not to be considered as limiting.

As used herein, proximal shall refer to a part or direction located away or furthest from a patient (upstream), while distal shall refer to a part or direction towards or located nearest to a patient (downstream). Also, a drug substance is used herein in an illustrative, non-limiting manner to refer to any substance injectable into the body of a patient for any purpose. Reference to a patient may be to any being, human or animal. Reference to a clinician may be to any person or thing giving treatment, e.g., a nurse, doctor, machine intelligence, caregiver, or even self-treatment.

FIGS. 1-12 illustrate an exemplary embodiment of a flow sensor system 200 of the present disclosure. Referring to FIGS. 1-12 , a flow sensor system 200 of the present disclosure includes two main assemblies which fit together prior to use: a flow sensor 210 and a base 220. In one embodiment, the flow sensor 210 can be a single-use flow sensor which is engageable with reusable base 220. The flow sensor system 200 is an intelligent injection port. The flow sensor system 200 is attachable to an injection site (“Y Site” or stop cock, for example) for manually administered IV injections.

The flow sensor system 200 of the present disclosure can reduce medication error at bedside during bolus delivery. The flow sensor system 200 of the present disclosure can also provide a record of and electronically measure bolus delivery, which allows monitoring bolus delivery and automatic documentation of bolus delivery as part of a patient's health record. The flow sensor system 200 of the present disclosure can also provide alerts when bolus delivery inconsistent with a patient's medical record is about to occur.

Referring to FIGS. 1-5B, in one embodiment, the base 220 is a non-sterile, reusable device that houses a battery, a scanner (either optical, mechanical, inductive, capacitive, proximity, or RFID), electronics, and wireless transmitter. In some embodiments, the base 220 is battery powered, and rechargeable. In some embodiments, each base 220 has a unique serial number imprinted on a surface of the base 220 or embedded therein that may be transmitted to a data system before use. The data system can be a local computer or tablet “Computer”, a cellular phone, another medical device, or a Hospital Data System.

In one embodiment, the base 220 is removably connectable to the flow sensor 210. Referring to FIGS. 5A and 6-9 , the base member 220 and the mechanical connection of the flow sensor 210 to the base member 220 is described. The base member 220 includes at least one deflectable wing tab 280 defining an opening for receiving at least a portion of the flow sensor 210 therein and for securing the flow sensor 210 within a portion of the base 220 prior to use. In one embodiment, a pair of wing tabs 280 secure the flow sensor 210 within the base 220. Optional gripping ribs 395 may be provided on an exterior profile for enabling a user to grasp the base portion 220.

An interior profile of the wing tab 280 may be provided with a catch 389 for corresponding engagement with a tab 189 provided on the flow sensor 210, as shown in FIG. 6 , to restrain the flow sensor 210 within the base 220, as will be discussed further herein. The wing tabs 280 may be flexible to the extent that they may be outwardly deflected to allow for passage of the flow sensor 210 thereover. The interior of the wing tab 280 may be provided with a pin cam 388 which allows a pin 188 of the flow sensor 210, as shown in FIG. 7 , to ride along such that the flow sensor 210 is moved proximally during assembly onto the base 220, to precisely align various optical and electrical components of the flow sensor 210 and the base member 220, as will be discussed further herein.

Referring to FIGS. 5B and 6-9 , the base member 220 and the electrical connection of flow sensor 210 to the base member 220 is described. The base 220 includes an activation/engagement button 350 which allows for an indication that the flow sensor 210 has been engaged with the base 220. In one embodiment, the activation/engagement button 350 signals to a microprocessor within the base 220 that a syringe has been properly engaged with the sensor 210 and its injection port 130.

The base 220 further includes a plurality of contacts 386 (FIG. 5B) for electrically engaging corresponding electrically active portions of the plurality of contact pins 385 (FIG. 7 ). A contour protrusion 488 surrounds at least a portion of the tongue 286. As shown in FIG. 7 , a bottom surface of the sensor 200 includes a pin seal 384 surrounding a plurality of contact pins 385 to prevent contamination, thus minimizing electrical disruptions. In some embodiments the plurality of pins 385 comprise a four pin connector with two pins electrically connected to each piezo element 150, 151, as will be discussed further. In other embodiments, the plurality of pins 385 comprise a six pin connector with two pins electrically connected to each piezo element 150, 151 and two pins electrically connected to a battery (not shown) in the flow sensor 210.

The base member 220 further includes a tongue 286 surrounded by a shoulder 486 having a plurality of contacts 386 for electrically engaging corresponding electrically active portions of sensor 200 and a charger 900 (FIG. 11A), as will be discussed herein.

Referring to FIGS. 1-4B, 6-9, and 13 , in one embodiment, the flow sensor 210 is a pre-sterilized disposable having an injection port 130 and a distal tubing connection, such as a Luer tip 109.

The flow sensor 210 may include a flow tube sub-assembly 10 consisting of a flow tube 100 having an outlet end 101 and an inlet end 102. The outlet end 101 may be provided in fluid communication with an outlet tubing 110 having an outlet connection 105 including a Luer tip 109 which may be optionally covered by a Luer cap 108. In a preferred embodiment, the outlet connection 105 is a plastic connector with a Luer tip 109, however, any suitable method to inject the medicament into a patient is envisaged to be within an aspect of an embodiment of the invention. For example, it may be desirable to replace the outlet connection 105 and tubing 110 with a needle for direct injection/infusion into a patient. Furthermore, it may be desirable to integrate the base 220 into a medication pen or infusion device for the delivery of insulin.

The inlet end 102 may be coupled to the reservoir of a medication pen or infusion reservoir. The inlet end 102 of the flow tube 100 may be provided in fluid communication with an injection port 130, and may optionally include a connection such as a threaded Luer lock 131 which is engageable with a source of a fluid to be injected. A pierceable septum 139 may be provided with the injection port 130 for maintaining sterility prior to use.

In a preferred embodiment, the injection port 130 is a plastic container with a split septum 139, however, any suitable method to inject the medicament through a flow sensor inlet 180 to a patient is envisaged to be within an embodiment of the present invention. For example, it may be desirable to replace the injection port 130 for direct connection to a medicament delivery device. In addition, it may be desirable to integrate the flow sensor inlet 180 to accept a direct fluidic connection to a medication delivery device.

In one embodiment, the flow tube 100 is comprised of a medical grade stainless steel and is approximately 50 mm long with a 1.0 mm inner diameter and a 1.6 mm outer diameter.

The flow sensor 210 also includes a first piezo element or upstream transducer 150 and a second piezo element or downstream transducer 151. The first piezo element 150 may be provided with an inlet fitting 180, as shown in FIG. 8 , for coupling with the injection port 130. Similarly, the second piezo element 151 may be provided with an outlet fitting 190, for coupling with the outlet tubing 110.

The flow sensor 210 can be supplied in a sterile package for a single patient use. In one embodiment, labeling is printed on the individual sterile package. In one embodiment, each flow sensor 210 has a unique serial number imprinted on a portion of its surface. In some embodiments, there are electronics in the flow sensor 210 which retain a unique identifier. These identifiers are transmitted either automatically or manually to a data system during use and data collection. In one embodiment, at the inlet end 102 of a flow sensor 210 the injection port 130 is a common needleless, Luer-Lok type. Typically, the inlet port or the injection port 130 is cleaned prior to giving an injection according to hospital policy. Additionally, flushing the flow sensor 210 with an IV fluid (e.g., normal saline syringe) is desirable before use. The injection port 130 on the flow sensor 210 typically supports up to 100 injections. In one embodiment, the flow sensor 210 has a male Luer-Lok connection, e.g., an outlet connection 105 having a luer tip 109, on a one-inch IV tubing pigtail at the outlet end 101. This male Luer-Lok connection may be attached to an IV line at a Y-site or IV manifold. Each flow sensor 210 has a unique serial number, however it may be desirable to only display a portion of the serial number on a portion of the exterior of the flow sensor 210. For example, the last 4 digits of the serial number may be imprinted on the surface next to its bar code. This human readable number is used to visually identify a flow sensor 210 within wireless range of communication of a computer. In some embodiments, the flow sensor 210 measures with an accuracy of ±5% for bolus volumes of 1.0 mL to 55 mL and ±20% for bolus volumes of 0.4 to 1.0 mL and has a dead-space volume of less than 0.3 mL.

Referring to FIGS. 11A-11D, in one embodiment, an optional separate charger 900 is compatible with the flow sensor system 200 and recharges a battery in the reusable base 220, if required, for reuse of the base 220. Referring to FIGS. 11A-11D, in one embodiment, the charger 900 includes a charger base 905 having an opening 925 for receiving the base 220, the opening 925 having charging pins 950 which engage corresponding contacts 386 in the reusable base 220. The charger 900 may include a sloped floor 930 for allowing disinfection liquid to drain therefrom. The device may also include elevated feet 999 to assist in drainage.

Reusable bases are typically supplied non-sterile and require disinfection and charging before use. It is preferred to disinfect each base 220 before first use. Typical commercial hospital disinfectants include alcohol-based quaternary ammonium, e.g., Metrex Research Cavi Wipes. In some embodiments, the base 220 can be used up to 500 times. Preferably, a rechargeable lithium ion battery is used within the base 220 and is not removable from the base 220. It is envisaged that a fully-charged base 220 will accommodate an entire patient case. In some embodiments, each base 220 is identified by labeling on the bottom of the device. Optionally, bases 220 are provided in individual boxes and each box is in a case package. The charger 900 may also include a power indicator 995. In one embodiment, when the base 220 is connected to a charger 900, up to four green light bars will illuminate on the top. The number of solid green light bars indicates the level of charge. A green blinking light on the base 220 will indicate it is recharging. In some embodiments, a useful life indicator is employed when the base 220 is connected to a charger 900 by use of a red light that indicates that the base 220 has exceeded its useful life. Optionally, on the Computer, an error message will display when a flow sensor system 200 whose useful life is completed is wirelessly connected to a tablet during patient setup. It would then be desirable to replace the base 220 with another and repeat the wireless connection to the Computer. Optionally, the flow sensor system 200 is provided in a mount which is an appliance that fits a standard Clarke socket to keep the flow sensor system 200 in place at the patient's bedside. Additionally, it may be desirable to clean and disinfect the charger 900 by using the procedure used for cleaning and disinfecting the base 220.

In one embodiment, the flow sensor system 200 supports injections using any Luer-lock type syringe. For example, referring to FIGS. 10A-10C, the flow sensor system 200 is compatible with a syringe 800 that is labeled. In one embodiment, the syringe 800 includes scale markings 805, a distal tip 810, a luer tip 815, a proximal end 820, a flange 825, a tip label 850 having human readable indicia 852 and machine readable indicia 854, a barrel label 860 having human readable indicia 862, and a plunger 890.

The base 220 of the flow sensor system 200 includes optics and a digital camera disposed within or behind a first window 360 (FIG. 2 ) capable of reading the machine readable indicia 854 provided on a label 850 of an encoded syringe. The first window 360 may be precisely aligned with Luer lock threads 131 present on the flow sensor 210 when the flow sensor 210 is assembled with the base 220, thus aligning the machine readable indicia 854 present on the label 850 on the syringe 800 during an injection cycle and/or medication determination cycle. The base 220 may further include a second window 370 (FIGS. 5A and 5B) having a light source for providing adequate lighting to the camera disposed within or behind window 360.

Additionally, the flow sensor system 200 is designed to work with encoded syringes that have a special barcode identifier on the Luer collar of the syringe, called “encoding”. Preferably, encoded syringes include commercially-available drugs in prefilled syringes with a special barcode that stores information about the medication contained within the syringe. Encoded syringes are ready-to-use, passive, and disposable. The flow sensor system 200 also accommodates syringes not having encoding. The encoding syringes store the drug name and concentration contained within the syringe. Additional characteristics such as drug source, container size, drug manufacturer source, drug category color, among others, may also be included. When an encoded syringe is attached to the injection port 130 of the flow sensor 210, this barcode information is read by a scanner in the base 220 wirelessly transmitted by the flow sensor system 200 to the data system. Preferably, the 2-D barcodes will be added to syringes during the filling process.

In one embodiment, the flow sensor system 200 contains a device to capture and transmit an image of a 2-D barcode on the Luer collar of the syringe, and wirelessly transmit this image to a “Computer”. Typically the Computer is a tablet computer communicating with multiple flow sensor systems 200. The 2-D barcode contains data, typically including the name and concentration of the drug in the syringe among other data. The Computer decodes this image, and displays and announces the drug attached. The barcode can contain the drug name and concentration. As the drug is injected, the flow sensor 210 in conjunction with the base 220 ultrasonically measures the volume of the injected drug and the time the drug was administered. This information may be stored in the flow sensor system 200 for later transmission to the Computer. The Computer uses this information to provide clinicians with an automated record of the drug name, concentration, volume, dose, and time of injection. The medication administration information is time stamped and displayed for clinical reference. Not all syringes used by the healthcare professional will contain a 2-D barcode. If a syringe without a 2-D barcode is inserted into the flow sensor system, the injection port 130, the flow sensor system 200 will prompt the user to manually enter the drug name and concentration into the computer. Information that is manually entered into the flow sensor system 200 is included in the patient medication record.

In one embodiment, the Computer can use a radio to wirelessly communicate with the flow sensor system 200 using an RF signal at 2.4 GHz to form a local medical device network. A number of flow sensor systems 200 and Computers may be used in the same vicinity such as a pre-operative care area or a post anesthesia care unit (PACU). Alert messages are communicated between the flow sensor system 200 and the Computer to advise the clinician of various operational characteristics of the flow sensor system 200. Some of these alerts inform the clinician of potential hazardous situations to allow user action to prevent harm to the patient or loss of medical data. Preferably, a lost wireless communication message will display when communication is lost between the flow sensor system 200 and the Computer. Preferably, all medication administration data from the flow sensor system 200 is transferred to the specific patient's medical record. In the event of a communication loss, medication administration data will be stored locally at the flow sensor system 200 and transferred to the Computer when communications are resumed.

The Computer may operate in a variety of modes. Typically the Computer has specialized flow sensor system 200 software for operations, a touch screen, and a wireless communications (Radio). It is typically mounted near an anesthetist or nursing work envelope and it may be removed for hand-held use. When the Computer is used in a hospital having a paper anesthesia record, the Computer supports features that assist with documenting the flow sheet portion and may help clinicians make the right decisions. In this configuration, the Computer complements the paper recordkeeping activities by tracking and displaying injections given through the flow sensor system 200. The Computer also enables clinicians to manually document other pertinent IV drug injection and infusion information.

In one embodiment, the software screens follow a three-step approach consisting of: (1) connecting the flow sensor system 200 to the Computer; (2) setting up a patient's flow sensor system 200 for use; and (3) viewing medication administration in multiple views.

In some embodiments, a view on the computer displays anesthesia based information in an anesthesia view, as shown in FIG. 14A. Preferably, this view provides information about the patient and displays drug name/concentration and dose for a current injection as well as a historical list of medications that have been delivered to the patient since the current case was opened. It may also include a listing of infusions given to the patient, if the clinician recorded them on the Computer. In this view, up to three injection bars display across the top of the screen, one corresponding to each wirelessly connected flow sensor system 200. Each injection bar is a real time representation of the medication being administered through an individual flow sensor system 200. When an encoded syringe is attached to a single flow sensor system 200, the injection bar displays the drug name and concentration. When a non-encoded syringe is attached, the injection bar will prompt the clinician to identify the medication and concentration being delivered. As the medication is being delivered, the volume pushed (in mL) and the corresponding dose displays in real time in the injection bar on the Computer display.

A flow sensor system 200 of the present disclosure may also provide optional medication history. For example, an anesthesia view can include a historical list of medications delivered to the patient organized by the surgical care area (medications given in the transition time between care areas, will post to the next care area) arranged in a flow sheet format. Preferably, this view includes all medications that were administered to the patient since the flow sensor system 200 was activated with the more recent medication administrations preferably at the bottom of the list. A scroll bar is enabled when the list exceeds the visible space on the screen of the Computer. Preferably, when a new medication is added, the medication list scrolls automatically so the new medication name is visible. In the view, preferably a color tile corresponding to American Society for Testing and Materials International (ASTM) standards and endorsed by the American Society of Anesthesiologists displays to the left of the drug name. Optionally, a clinician may also specify that an admixture (mixed medication), or a diluted or reconstituted medication was delivered. Optionally, the Computer displays a case header which lists the patient name, date of birth, age in years, medical record number, and patient identification number. Optionally, the Computer will indicate that the patient has “no known allergies”. Preferably, if the patient has allergies, that text is replaced by a button, more preferably, and the button has a number on the button that indicates the number of allergies.

A flow sensor system 200 of the present disclosure may also provide an optional tabular view, as shown in FIG. 14B. For example, the tabular view is an alternate view for the clinician to interact with the flow sensor system 200. Similar to the anesthesia view described above, this view provides information about the patient and displays drug name/concentration and dose for a current injection as well as a historical list of medications that have been delivered to the patient. It may also include a listing of infusions given to the patient, if recorded by the clinician. The tabular view has many of the features of the anesthesia view; however, it is arranged in a tabular format. Preferably, the column headings in this view include time administered, medication with concentration, dose, and unit total. Optimally, the medications are displayed in reverse chronological order with most recent medication administered at the top of the list.

In one embodiment, the Computer provides two types of messages: (1) “Clinical” and (2) “System”. Clinical messages are alerts and reminders that relate directly to an aspect of patient care delivery (e.g. contraindication or a reminder that it may be time to re-dose antibiotics). System messages provide status on relevant system operating parameters.

Messages provide instructions and a button for acknowledging or resolving. Messages display on the Computer until they are acknowledged or are no longer clinically relevant. Messages can be answered any time during a case. Prior to pausing or closing a case, the clinician is prompted to respond/answer unresolved medication messages generated during the case. An allergy alert illuminates the flow sensor system 200 and displays on the Computer when a clinician attaches an encoded syringe or selects a medication for a non-encoded syringe to which the patient has a known allergy. Optionally, this message may be overridden.

When dosing antibiotics, preferably the Computer tracks elapsed time since an antibiotic was last administered and displays and announces an antibiotic redosing message if the configured redosing interval has elapsed. The redosing interval is individual to each antibiotic, and it is configured in the drug library of the Computer or Gateway (further described below). In one embodiment, the flow sensor system 200 does not prevent or block the injection of a medication. In other embodiments, the flow sensor system 200 is able to block the injection of a medication.

In one embodiment, the Computer posts a message when the volume injected through the flow sensor system 200 was not measured. This may occur when the volume measured is outside of a range of sensing of the flow sensor system 200.

Optionally, the Computer wirelessly communicates bi-directionally with a software application that acts as a central hub to which all Computers (and thus multiple upon multiples of flow sensor systems 200) are connected, the “Gateway”. Preferably, the Gateway is also connected to the hospital's other networked information systems. The Gateway allows all Computers to share patient case information such as drug name, dose, and time delivered with each other, and with the hospital's networked information systems. The Gateway also allows Computers to receive patient information such as patient drug allergies and patient drug orders from other networked hospital information systems.

Utilizing the flow sensor system 200 of the present disclosure encompasses the steps of connecting the flow sensor 210 to the patient's catheter or injection port (Y-site). Preferably, the flow sensor 210 and line is flushed. The flow sensor 210 is keyed to an individual patient using a unique serial number and the base 220 records medication administration through the port at the inlet end 102 of the flow sensor 210.

When a syringe 800 is attached to the injection port 130, the flow sensor system 200 identifies the medication and concentration for an encoded syringe by optically imaging and decoding a barcode on the Luer-Lok collar of the syringe 800. This information is wirelessly transmitted to the Computer. Preferably, the Computer displays and audibly announces the drug attached. The Computer also may perform allergy safety checks based on the patient's medical record.

In one embodiment, as the drug is injected, the flow sensor system 200 measures the volume dosed ultrasonically. The flow sensor system 200 wirelessly sends volume measurement information to the Computer. The Computer uses this information to provide clinicians with a medication administration record which is time stamped and displays for clinical reference during surgical procedures. Manually entered infusions and other information pertaining to non-encoded drug injections may be included in the patient medication record in the Computer and the Gateway. The Computer wirelessly communicates with the Gateway on the hospital network, and it may send medication administration to Hospital Information Systems, when configured, for reporting and electronic recordkeeping purposes. Preferably, the Computer wirelessly communicates with the existing Hospital Network using a standards based IEEE 802.11a/b/g/n enterprise WLAN network. The Gateway software and accompanied database will be a part of the hospital's enterprise information system. A number of Computers may be connected to the healthcare enterprise wireless network and to the intended Gateway software and database. Preferably, the Gateway and accompanied database provides a list of patients for the user to select and a formulary library of medications and fluids for injection or infusion. In one embodiment, actual medication and fluid administration data are sent to the Gateway and accompanied database for recordkeeping. Once recorded on the Gateway and accompanied database these data are preferably available in other care areas when the patient is transferred and the flow sensor system 200 is wirelessly connected to a Computer. Preferably, in the event of a communication loss, medication administration data will not be sent to the Gateway and therefore not available in the next care area.

Referring to FIGS. 1-12 , use of a flow sensor system 200 of the present disclosure will now be described. First, preparing the flow sensor system 200 for an injection will be discussed.

In one embodiment, the flow sensor system 200 is prepared, attached to an IV line, and assembled for use. Preferably, there are pre-printed instructions located on the flow sensor 210 sterility pouch. First, a user obtains a flow sensor 210 in its sterile packaging and a fully-charged and disinfected reusable base 220. In one embodiment, a fully-charged base 220 has sufficient power for at least 24 hours of use under typical conditions. Optionally, the base 220 provides a visual indication of charge level via a display.

Next, the flow sensor 210 is flushed with sterile IV fluid before attaching to the Y-site. In one embodiment, the flow sensor 210 is flushed with more than 8 mL of sterile IV fluid. After flushing, a user can visually inspect the IV line for leaks, air, or blockage.

Next, a user attaches the flow sensor 210 to the base 220 by joining the flow sensor 210 (tubing side) and base 220 front sections first, and then snapping the two together. Preferably, an audible snapping sound is heard to indicate a secure connection between the flow sensor 210 and the base 220. In one embodiment, connecting the flow sensor 210 to the base 220 automatically powers on the flow sensor system 200. In one embodiment, the connection of the flow sensor 210 to the base 220 is verified by a blinking light on the base 220. In other embodiments, other indicators may be used. Catch 389 of the base 220, shown in FIG. 5A, engages tab 189 of the flow sensor 210, shown in FIG. 6 , to restrain the flow sensor 210 with the base 220 prior to initiation of an injection. In one embodiment, deflection of the wing tab or wing tabs 280 moves tab 189 with respect to catch 389 to initiate engagement or disengagement therewith. When the flow sensor 210 is assembled to the base 220, a cantilever 650 provided on the base 220, such as a lower housing 212 as will be discussed herein, is aligned with button 350 provided on the base 220. The interior of the wing tab 280 may also be provided with a pin cam 388 which allows pin 188 of the flow sensor 210, as shown in FIG. 6 , to ride along such that the flow sensor 210 is moved proximally during assembly onto the base 220. During engagement, tongue 286 shown in FIG. 5A, is engaged within an opening 285 shown in FIG. 7 . With continued reference to FIGS. 5A and 7 , a vault 485 having ribs 487 on the flow sensor 210 as shown in FIG. 7 , has a corresponding exterior profile taken with the shoulder 486 of the base 220, as shown in FIG. 5A, to engage for alignment of the first window 360 to precisely align with Luer lock threads 131 when the flow sensor 210 is assembled to the base 220.

In some embodiments, where appropriate, the flow sensor system 200 is secured to a surface in preparation for giving injections. For example, in some embodiments, referring to FIG. 12 , a mount 1100 is used to secure the flow sensor system 200 to a surface. During this step, it is important to avoid kinks in the line between the flow sensor system 200 and IV line.

The flow sensor system 200 is now ready for delivery of IV medications. Preferably, any medications given through the flow sensor system 200 will be recorded in the electronic base 220 memory. In one embodiment, in the event of a flow sensor system 200 failure (excluding the IV fluid pathway), the flow sensor system 200 will still allow standard medication or fluid delivery through the port.

Next, giving an injection using the flow sensor system 200 will be discussed. First, the injection port 130 is cleaned by swabbing the hub according to normal hospital procedure. Next, a syringe 800 can be attached to the injection port 130 of the flow sensor 210 by completely turning the syringe 800 until the syringe 800 stops, i.e., a secure connection between the syringe 800 and the injection port 130 is made. Ideally, the caregiver double checks each medication name and concentration on the syringe 800 prior to attachment to the injection port 130 to assure the correct medication is given. During the injection cycle and/or medicament determination cycle, when syringe tip 810 contacts a syringe protrusion 652, as shown in FIG. 4B, the cantilever 650 is deflected radially from the longitudinal axis of the syringe 800. A pad protrusion 651 depresses button 350 on the base 220 and the button 350 signals the microprocessor to act.

Next, the drug and concentration displayed and announced by the Computer is verified as the intended drug and concentration. In one embodiment, the base 220 will alert the caregiver that an allergy is detected by an alert, for example, by flashing red, green, and yellow lights if a medication allergy is detected. Optionally, the Computer calculates a potential allergy reaction and provides an alert when any of these conditions is true: (1) an encoded syringe is inserted into the flow sensor 210 and the drug matches the patient's allergy profile; or (2) a non-encoded syringe is inserted into a flow sensor 210 and you select a drug from the select medication screen that matches the patient's allergy profile. If one of these conditions is true, the allergy alert flag on the Computer configuration is turned on.

In one embodiment, there is no check valve in the flow sensor 210, nor is one needed to use the flow sensor 210 safely and effectively. Typically, the flow sensor system 200 measures 0.4 mL to 55 mL per injection. If the injection flow rate is slow or a small volume is delivered (<0.4 mL) preferably an alert will display on the Computer. Optionally, an alarm is configured to detect rapid delivery from a large volume, e.g., 50 mL syringe. In this case, an alert is provided to check the dose.

In one embodiment, an indicator 375, such as a series of four LED indicators, turn on in sequence to indicate to the user that fluid is moving through the flow sensor 210. When base 220 is mounted in the charger 900, the indicator 375 can indicate a level of battery charge of the base 220.

In one embodiment, it is preferred to follow all medication injections through the flow sensor system 200 with an encoded normal saline flush syringe to ensure the full dose of medications reaches the patient, especially when successively delivering two incompatible medications. Optionally, the flow sensor system 200 records such saline flush activity.

In one embodiment, injections are recorded whether or not the flow sensor system 200 is wirelessly connected to the Computer. The base 220 stores injection information in its memory and transmits this information upon wireless connection to the Computer.

In one embodiment, the Computer can accommodate multiple flow sensor systems 200 connected to one patient at a time. An additional flow sensor system 200 may be added at any time during a patient's treatment. When a flow sensor system 200 is connected to a Computer and there is no syringe attached to the flow sensor 210, the active injection bar reads “Sensor Connected, No syringe”. On the Computer display, a battery status icon in the upper right corner of the injection bar indicates the battery charge level of the base 220 to which the flow sensor 210 is connected. For each injection a caregiver may enter a comment on the Computer.

The present disclosure provides a flow sensor sub-assembly for sensing flow of a fluidic medicament. The flow sensor sub-assembly includes a first spring contact and a second spring contact. In one embodiment, the spring contacts are secured to a base that has a circuit for conducting an electrical signal to and from the spring contacts to a microprocessor. The first spring contact is in electrical communication with a first piezo element and the second spring contact is in electrical communication with a second piezo element. The first spring contact has a first contact force against the first piezo element and the second spring contact has a second contact force against the second piezo element, and the first contact force is equivalent to the second contact force. The present disclosure also provides a circuit board for interfacing to a flow sensor having a plurality of piezo elements for transmitting a flow signal indicative of flow of a fluidic medicament.

A spring contact of the present disclosure provides electrical contact to a piezo element. For example, a spring contact of the present disclosure provides electrical contact to a silvered surface of a piezoelectric crystal. Furthermore this contact provides a spring force selected to accommodate assembly tolerances, temperature variation, electrical requirements, material selection for a long life to silver, and assembly features for a single-sided printed circuit board assembly (PCBA) attachment. The flow sensor sub-assembly of the present disclosure provides for four contacts used in a sensor to have the same force on both surfaces of each of two piezo elements, such as crystals, in a single transducer.

A circuit board of the present disclosure provides a single-sided PCBA. The single-sided PCBA of the present disclosure provides a lower cost design than conventional double-sided PCBA designs. The circuit board of the present disclosure also provides a means to maintain mechanical loading of the crystal contacts when the transducer is inserted to the PCBA.

Electrical contacts to the ultrasound crystal have previously been accomplished by soldering wires to a silver coating. A spring contact of the present disclosure provides a cost reduction method by using the spring contacts to connect to the crystal. In particular, a single-sided printed circuit board (PCB) of the present disclosure provides for a lower cost design and a through hole contact design. The design of the present disclosure includes the force exertion by the spring constant, dimension of separation between contacts, material type of the springs, the range of forces necessary, and tolerance control of forces exerted by the spring contact, which are all important to eliminate soldering. If soldering is too hot, it often takes silver off the surface of the crystal. Another problem with soldering is leaving too much solder behind, which may also cause loading of the ultrasonic physical characteristics. Consistent electrical and physical contact (repeatability) for both crystals is important as well as sensor to sensor calibration. The forces cannot be too high (potential for a slurry to develop) or too low (variable impedance).

The flow sensor sub-assembly of the present disclosure provides a high volume, disposable design with benefits for its cost, reliability, and repeatability. The flow sensor sub-assembly of the present disclosure allows for future automation features. The flow sensor sub-assembly of the present disclosure provides for maximal tolerance designed in conditions. The flow sensor sub-assembly of the present disclosure is able to fit inside the housing of a flow sensor 210.

Referring to FIGS. 8, 13, and 15-17 , a flow tube sub-assembly 10 includes a flow tube 100, an outlet connection 105, an outlet tubing 110, an injection port 130, a first piezo element or upstream transducer 150, a second piezo element or downstream transducer 151, an inlet fitting 180, an outlet fitting 190, a fitting 185, and/or an absorber sheath 400 or 500. The flow tube sub-assembly 10 can be part of the flow sensor 210 sub-assembly of the present disclosure that is contained within the flow sensor housing 211, 212. A portion of the flow sensor housing 212 is coupled to a flow sensor base 220 which contains a microprocessor and a circuit that includes connecting pins for providing an electrical signal from the flow sensor 210 sub-assembly to the microprocessor within the flow sensor base 220. The flow sensor 210 sub-assembly including the flow tube sub-assembly 10 can be disposed after the flow sensor 210 sub-assembly including the flow tube sub-assembly 10 is used to sense the flow of at least one fluidic medicament. The flow sensor base 220 can be used with a plurality of different flow sensor 210 sub-assemblies including a plurality of different flow tube sub-assemblies 10. In one configuration, the sub-assembly 10 for a flow sensor 210 may be utilized as a flow sensor 210 and inserted directly into the base 220, rather than as a component of a housing 211, 212 of the flow sensor 210.

As shown in FIG. 13 , the flow tube 100, through which a medicament flows, has a flow tube inlet 102 and a flow tube outlet 101. The flow tube inlet 102 may be coupled to the reservoir of a medication pen or infusion reservoir. As described herein, in some embodiments, the flow tube inlet 102 of the flow tube 100 may be provided in fluid communication with the injection port 130.

The flow tube 100 includes an inner flow tube 100 and end fittings, e.g., the inlet fitting 180 at the inlet end 102 and the outlet fitting 190 at the outlet end 101, for securing the flow tube 100 to the respective end fittings 180, 190 at the end faces of the flow tube 100. Referring to FIGS. 18A-D and 19A-D, a fitting adhesive 186 can be used to bond the flow tube 100 Fitting-Tube Interface Zone 157 to the end fittings 180, 190 so that energy from the first and second piezo elements 150 and 151 is transmitted more optimally across the Fitting-Tube Transmission Zone 158. The fitting adhesive 186 dampens the energy transfer across the Fitting-Tube Interface Zone 157, while minimizing the losses at the Fitting-Tube Transmission Zone 158. Preferably, the fitting adhesive 186 dampens out of phase and/or rogue vibrations induced in the end fittings 180, 190 by the transmission of sound energy between the first and second piezo elements 150, 151 and the end fittings 180, 190. Preferably, the fitting adhesive 186 is a low viscous, medical grade adhesive, able to flow via capillary action into fill gaps, e.g., as shown in FIGS. 18B and 19B. In the Fitting-Tube Transmission Zone 158, an air gap between the outside diameter and the flow tube 100 and the end fittings 180,190 may be desirable as this may reduce or prevent out of phase and/or rogue energy transmission which interferes with the main signal to be detected by the microprocessor. However, regardless of the configuration of the Fitting-Tube Transmission Zone 158, in some embodiments it may be desirable that the flow tube 100 is in minimal contact with a sidewall of the flow tube 100 and in maximal contact at the end fittings 180, 190 at the end faces of flow tube 100. During assembly this is accomplished by application of a longitudinal biasing force on flow tube 100 in a direction toward the end fittings 180, 190 as fitting adhesive 186 permanently bonds the flow tube 100 and the end fittings 180, 190. Preferably, the fitting adhesive 186 maintains its desirable properties after sterilization. The material of the absorber may be one of any polymers or elastomers, such as polyvinylchloride, silicone rubber, and the like. In one embodiment, the material of the absorber may be flexible in nature and have a lower durometer than that of the flow tube. By providing an absorber having a different and lower durometer than that of the flow tube, the vibrations are maintained within the absorber, rather than passed into the flow tube. At the interface of the absorber and the flow tube is a boundary, and the behavior of energy at the boundary has essentially two useable factors: reflection and transmission/refraction. The reflected and transmitted waves will obey Snell's Law.

The first piezo element 150 is arranged at an upstream position of the flow tube 100 and the second piezo element 151 is arranged at a downstream position of the flow tube 100. The first and second piezo elements 150 and 151 are configured to transmit a flow signal indicative of a flow of the fluidic medicament in the flow tube 100. In an embodiment, the first piezo element 150 and the second piezo element 151 are annular in shape and encircle the flow tube 100 at each respective mounting point. In one embodiment, the first piezo element 150 and the second piezo element 151 are mounted apart a pre-selected distance from each other. In one embodiment, each of the spring contacts 750 are secured to a base, e.g., a circuit board 700. The circuit board 700 includes a circuit for conducting an electrical signal to and from the spring contacts 750 to a microprocessor. The first spring contact 750 is in electrical communication with the first piezo element 150 and the second spring contact 750 is in electrical communication with the second piezo element 151. The first spring contact 750 has a first contact force against the first piezo element 150 and the second spring contact 750 has a second contact force with the second piezo element 151. In one embodiment, the first contact force is equivalent to the second contact force. Preferably, the upstream transducer 150 and downstream transducer 151 are interchangeable, however, it is envisaged that they may be purposefully constructed for their respective positions on the flow sensor sub-assembly 10. In another embodiment, circuit board 700 can contain a non-volatile memory containing the serial number of the sensor 210, calibration data and/or flow calculation constants for communication to the electronic microprocessor of the base 220.

The first and second piezo elements 150, 151 can be mounted to the end fittings 180, 190 as shown in FIG. 13 . For example, referring to FIGS. 18A-D and 19A-D, a transducer adhesive 156 can be used to bond the first and second piezo elements 150, 151 to the end fittings 180, 190 so that energy from the transducers 150, 151 is transmitted optimally across the Transducer-Fitting Transmission Zone 159. The adhesive can increase or maximize the energy transfer across the Transducer-Fitting Transmission Zone 159, while reducing or minimizing energy losses. Preferably, the transducer adhesive 156 facilitates the transmission of sound energy between the first and second piezo elements 150, 151 and the end fittings 180, 190. The transducer adhesive 156 can be a moderately viscous, medical grade adhesive. Air gaps between the first and second piezo elements 150, 151 and the end fittings 180, 190 can be eliminated to enable more efficient sound energy transmission. Preferably, the transducer adhesive 156 maintains its properties after sterilization.

Referring now to FIG. 15 , in some embodiments the flow tube sub-assembly 10 need not include an absorber sheath 400 or 500. The flow tube 100 may be exposed between the inlet fitting 180 and the outlet fitting 190. An outside diameter (OD) of the flow tube 100 can be varied to achieve different levels of attenuation of a drive signal, for example, as described below with respect to example cases 5 and 6. The flow tube 100 can comprise a steel tube.

Referring again to FIG. 13 , and with additional reference to FIG. 17 , the absorber sheath 500 can encircle the flow tube 100. The flow tube 100 can be a continuous, unbroken flow tube 100. In some embodiments, there may be a gap between the absorber sheath 500 and the inlet fitting 180 exposing a portion of the flow tube 100 at the inlet end 102 and/or a gap between the absorber sheath 500 and the outlet fitting 190 exposing a portion of the flow tube 100 at the outlet end 101. For example, the absorber sheath 500 may be positioned about 6 mm away from the inlet fitting 180 and about 6 mm away from the outlet fitting 190.

The absorber sheath 500 comprises a material with an acoustical transmission rate different than an acoustical transmission rate of a material of the flow tube 100. For example, the flow tube 100 can comprise a stainless steel material, and the absorber sheath can comprise a plastic material, a PVC material, an elastomer material, a 70A Shore hardness medical grade silicone rubber material, or a heat shrink tubing material.

In an embodiment, as shown in FIGS. 18A-D, the absorber sheath 500 can be heat shrunk onto an outside diameter of the flow tube 100. The absorber sheath 500 can comprise a heat shrink material, such as an EPS-300 Heat Shrink or a MFP Heat Shrink described below with respect to example cases 3 and 4. For example, an outside diameter of the absorber sheath 500 can be about 2.4 mm with a wall thickness of about 0.25 mm for a cross-linked, thin-walled, heat shrinkable tubing fabricated from polyvinylidene fluoride, which when heated in excess of 347° F. (175° C.) rapidly shrinks to a skintight fit around the flow tube 100. In another embodiment, the absorber sheath 500 can comprise a thin-wall, flexible tubing having an integral, adhesive-lined construction made from polyolefin with an internal layer of thermoplastic adhesive and having a heat-shrinkable outer wall that is selectively cross-linked, which when heated in excess of 121° C. (250° F.), shrink fits the OD of the flow tube 100 and melts the adhesive lining to bond the absorber sheath 500 to the flow tube 100. In some embodiments, it may be preferable that the heat shrink material of the absorber sheath 500 forms a flexible bond with the flow tube 100. In other embodiments, it may be preferable that the heat shrink material of the absorber sheath 500 forms a rigid bond with the flow tube 100. As shown by the progression of FIGS. 18A though 18D, the end fittings 180, 190 may be adhered to the flow tube 100 before the absorber sheath 500.

In another embodiment, as shown in FIGS. 19A-D, the absorber sheath 500 can be adhered to the flow tube 100 with an absorber adhesive 510. The absorber adhesive 510 can be acoustically transparent. In some embodiments, it is preferable that the absorber adhesive 510 forms a flexible bond with the flow tube 100. In other embodiments, it is preferable that the absorber adhesive 510 forms a rigid bond with the flow tube 100. In some examples, the absorber adhesive 510 can be similar to or the same adhesive as the fitting adhesive 186 or the transducer adhesive 156. As shown by the progression of FIGS. 19A though 19D, the absorber sheath 500 can be adhered to the flow tube 100 with the absorber adhesive 510 before the end fittings 180, 190.

Referring now to FIG. 16 , in some embodiments, the flow tube 100 may comprise a non-continuous flow tube. An upstream portion of the flow tube 100 including the inlet end 102, e.g., a first flow tube 100 a, may be spaced apart from a downstream portion of the flow tube 100 including the outlet end 101, e.g., a second flow tube 100 b. The first flow tube 100 a may be connected to the second flow tube 100 b by an absorber sheath 400. Each of the first flow tube 100 a and the second flow tube 100 b have a respective flow tube inlet and a respective flow tube outlet, and an outside diameter. The absorber sheath 400 can connect the flow tube outlet of the first flow tube 100 a to the flow tube inlet of the second flow tube 100 b with a gap therebetween such that the medicament flows through at least a portion of the absorber sheath 400.

The absorber sheath connector 400 can be heat shrunk or adhered with the absorber adhesive 510 to at least a portion of each of the first flow tube 100 a and the second flow tube 100 b, e.g., to the flow tube outlet of the first flow tube 100 a and to the flow tube inlet of the second flow tube 100 b. The materials, properties, and connections of the absorber sheath 400 can be similar to or the same as the absorber sheath 500 and, therefore, a more detailed description thereof is omitted in the interest of brevity. In an embodiment, the absorber sheath 400 can comprise a 70A Shore hardness medical grade silicone rubber material and is positioned at an anti-node location that is approximately 2.5 mm from a center of the flow tube 100 that comprises a steel material.

The outlet end 101 of the flow tube 100 may be provided in fluid communication with an outlet tubing 110 having an outlet connection 105. The outlet fitting 190 can couple the outlet end 101 of the flow tube 100 to the outlet tubing 110. The outlet tubing may be coupled to the fitting 185 at its other end, and the fitting 185 can connect the outlet tubing 110 to the outlet connection 105. The fitting 185 can be bonded to the outlet tubing in a similar or the same manner as the end fittings 180, 190 are bonded to the flow tube 100.

A simulation analysis was performed in SolidWorks Simulation 2012 modelling the flow of water through a flow tube 100 of a flow tube sub-assembly 10 according to preferred and non-limiting embodiments. The simulation analysis was performed using the boundary conditions and material properties listed in Tables 1A and 1B below and utilizing a Parabolic Tet Mesh with approximately 96,000 Nodes and approximately 63,000 Elements. The mesh was simulated without consideration for any adhesive between a steel flow tube 100 and the inlet and outlet fittings 180, 190. Furthermore, the simulation analysis assumed that the inside surface of the inlet fitting 180 is fixed. The inlet crystal of the first piezo element 150 was modeled to have a sinusoidal displacement applied in two directions, axially along the axis of flow in the flow tube 100 and radially at a Frequency of 533 kHz. A Displacement Magnitude of the crystal was set at 0.001. Each material of the flow tube sub-assembly 10 is given a specific damping ratio in the simulation analysis. In each example case of the simulation analysis described below, attenuation is calculated by the reduction in displacement transverse to the longitudinal axis of the flow tube 100.

TABLE 1A Material Properties Material Ultem HU101 Loctite M31CL PZT Stainless Steel Component Inlet and Outlet Fittings Crystal Bond Crystal Flow Tube Units Elastic Modulus 3.58E+09 6.89E+08 6.60E+10 1.93E+09 N/m² Poissons Ratio 0.3 0.3 0.3 0.3 N/A Mass Density 1270 1100 7650 8000 kg/m³ Tensile Strength 1.05E+08 5.52E+07 3.55E+07 5.50E+08 N/m² Yield Strength 1.05E+08 5.52E+07 3.55E+07 N/m² Thermal Expansion Coefficient 5.00E−05 6.80E−05 1.50E−06 1.60E−05 /° C. Thermal Conductivity 0.22 0.151 1.8 16.3 W/(m − K) Specific Heat 1400 1200 350 500 J/(kg − K) Damping Ratio 0.02 0.02 0.05 0.01 N/A

TABLE 1B Material Properties Material Water 70A Silicone 3M EPS-300 3M MFP Component Water Absorber Sheath Heat Shrink Heat Shrink Units Elastic Modulus 2.20E+09 5.00E+07 1.17E+08 8.48E+08 N/m² Poissons Ratio 0.49 0.49 0.3 0.3 N/A Mass Density 1000 2300 1300 1700 kg/m³ Tensile Strength 3.00E+07 5.50E+06 1.44E+07 3.79E+07 N/m² Yield Strength N/m² Thermal Expansion Coefficient 6.90E−05 /° C. Thermal Conductivity 0.6 2.55 W/(m − K) Specific Heat 4200 1300 J/(kg − K) Damping Ratio 0.001 0.05 0.05 0.05 N/A

The results of the simulation analysis for each example case are provided in Tables 2 and 3 below. Example case 1 corresponds to an embodiment including a flow tube without an absorber sheath 500, e.g., as shown in FIG. 15 . Example case 2 corresponds to an embodiment including a non-continuous flow tube 100 and an absorber sheath 400, e.g., as shown in FIG. 16 . For example case 2, the absorber sheath 400 comprises 70A Shore hardness medical grade silicone rubber and is positioned at an anti-node location which is approximately 2.5 mm from the center of the steel flow tube 100. Example cases 3 and 4 correspond to an embodiment including a flow tube 100 and an absorber sheath 500, e.g., as shown in FIG. 17 . The absorber sheath 500 is heat shrunk to the flow tube 100 in example cases 3 and 4, wherein the absorber sheath 500 is an EPS-300 heat shrink in example case 3 and a MFP heat shrink in example case 4. Example cases 5 and 6 correspond to embodiments where the outside diameter (OD) of a steel flow tube 100 is modified. The headings across the top of Table 2 correspond to the following: Case Number, Component(s), Total Mass (g), Total Bending Stiffness (N/m), First Natural Frequency (rad/s), First Natural Frequency (Hz), Number of Harmonics to get close to 533 kHz (Hz), and Difference between Harmonic and 533 kHz (Hz).

TABLE 2 Total Total Bend First Nat. First Nat. # of Harms. to get Harm. closest Diff. btwn Harm. Case Components Mass (g) Stiff (N/m) Freq. (rad/s) Freq. (Hz) dose to 533 kHz (Hz) to 533 kHz (Hz) and 533 kHz (Hz) 1 Steel Tube Only (no 0.066 1002.4 123.2 19.6 27174 532994.4 5.6 absorber sheath) 2 Non-Continuous Steel 0.17 5.14E+−2 55.0 8.8 60890 532999.4 0.6 Tube and Absorber 3 Steel Tube and 0.39 1039.9 51.6 8.2 64854 533001.4 −1.4 EPS-300 Heat Shrink 4 Steel Tube and 0.17 1047.3 78.5 12.5 42668 533002.0 −2.0 MFP Heat Shrink 5 Steel Tube w/1.1303 mm 0.012 114.1 97.5 15.5 34343 533004.1 −4.1 OD (no absorber) 6 Steel Tube w/1.3462 mm 0.034 412.3 110.1 17.5 30412 533006.6 −6.6 OD (no absorber)

TABLE 3 Max Part Displacement Case # Case Description Description (mm) % Attenuation 1 Assembly w/Steel Tube Flow Tube 7.281E−06  N/A Only (no absorber sheath) 2 Assembly w/Non-Continuous Inlet Flow Tube 2.903E−06  60.1% Steel Tube w/Absorber 2 Assembly w/Non-Continuous Outlet Flow Tube 1.874E−06  74.3% Steel Tube w/Absorber 3 Assembly w/Steel Tube Flow Tube 3.68E−06 49.5% w/EPS-300 Heat Shrink 4 Assembly w/Steel Tube Flow Tube 2.65E−06 63.6% w/MFP Heat Shrink 5 Assembly w/Steel Tube Flow Tube 1.02E−05 −40.1% w/1.1303 OD 6 Assembly w/Steel Tube Flow Tube 2.66E−06 63.5 w/1.3462 OD

As shown in Tables 2 and 3, modifications to the flow tube in example cases 2, 3, 4, and 6 caused an attenuation of the drive signal. All of the cases had harmonics relatively close to 533 kHz. A preferable flow tube sub-assembly 10 which attenuates the drive signal is provided in example cases 3 and 4. More preferably, cutting the tube and adding absorber sheath 400 as demonstrated by example case 2 attenuates the drive signal by between approximately 60 and 75%. The outside diameter (OD) of the sheath in example case 4 was approximately 2.4 mm with a wall thickness of approximately 0.25 mm, while the OD of the sheath in example case 3 was approximately 3.5 mm with a wall thickness of about 0.5 to 1 mm. A tubing used for the absorber sheath 400 in example case 4 is a cross-linked, thin-walled, heat-shrinkable tubing fabricated from polyvinylidene fluoride, which when heated in excess of 347° F. (175° C.) rapidly shrinks to a skintight fit around the flow tube 100. A tubing used for the absorber sheath 400 used in example case 3 is a thin-wall, flexible tubing having an integral, adhesive-lined construction. The tubing in example case 3 is made from polyolefin with an internal layer of thermoplastic adhesive, wherein the heat-shrinkable outer wall is selectively cross-linked. When heated in excess of 121° C. (250° F.), the tubing of example case 3 tubing shrinks to fit the OD of the flow tube 100 and melts the adhesive lining to bond the sheath 500 to the flow tube 100.

While this disclosure has been described as having exemplary designs, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims. 

What is claimed is:
 1. A flow sensor sub-assembly comprising: a flow tube; and an absorber sheath encircling said flow tube.
 2. The flow sensor sub-assembly according to claim 1, wherein said absorber sheath is comprised of a material with an acoustical transmission rate different than an acoustical transmission rate of said flow tube.
 3. The flow sensor sub-assembly according to claim 1, wherein the flow tube has a flow tube inlet and a flow tube outlet, the flow sensor sub-assembly further comprising: an inlet fitting at the flow tube inlet; an outlet fitting at the flow tube outlet; a first piezo element; and a second piezo element, wherein the first and second piezo elements are respectively mounted to the inlet fitting and the outlet fitting.
 4. The flow sensor sub-assembly according to claim 3, wherein an upstream end and a downstream end of the absorber sheath are respectively spaced apart from the inlet fitting and the outlet fitting by a distance of about 6 mm.
 5. The flow sensor sub-assembly according to claim 3, wherein the flow tube comprises a non-continuous flow tube, wherein an upstream portion of the flow tube including the inlet fitting is spaced apart from a downstream portion of the flow tube including the outlet fitting, and wherein the upstream portion of the flow tube is connected to the downstream portion of the flow tube by the absorber sheath with a gap between the upstream portion of the flow tube and the downstream portion of the flow tube.
 6. The flow sensor sub-assembly according to claim 1, wherein said absorber sheath is one of heat shrunk onto an outside diameter of said flow tube and adhered to said flow tube with an adhesive.
 7. The flow sensor sub-assembly according to claim 6, wherein said absorber sheath is adhered to said flow tube with the adhesive, and wherein said adhesive is acoustically transparent.
 8. The flow sensor sub-assembly according to claim 1, wherein said flow tube is a stainless steel material.
 9. The flow sensor sub-assembly according to claim 1, wherein said absorber sheath is one of a plastic material and a PVC material.
 10. The flow sensor sub-assembly according to claim 1, further comprising: a flow sensor base, wherein said flow sensor sub-assembly is contained within a flow sensor housing, wherein said flow sensor housing is coupled to the flow sensor base which contains a microprocessor and a circuit for providing an electrical signal from said flow sensor sub-assembly to said microprocessor within said flow sensor base, wherein said flow sensor sub-assembly is disposed after said flow sensor sub-assembly is used to sense a flow of at least one fluidic medicament, and wherein the flow sensor base is used with a different flow sensor sub-assembly.
 11. A flow sensor sub-assembly comprising: a flow tube sub-assembly having: a first flow tube and a second flow tube; and an absorber sheath connecting said first flow tube to said second flow tube, wherein said absorber sheath encircles said first flow tube and said second flow tube.
 12. The flow sensor sub-assembly according to claim 11, wherein said absorber sheath connects said first flow tube to said second flow tube with a gap therebetween.
 13. The flow sensor sub-assembly according to claim 11, wherein the first flow tube and the second flow tube each have a respective flow tube inlet and a respective flow tube outlet, and an outside diameter, wherein the flow tube sub-assembly further comprises: a first piezo element arranged at an upstream position of the flow tube sub-assembly and a second piezo element arranged at a downstream position of the flow tube sub-assembly; and end fittings adapted for securing each flow tube to the end fittings, wherein the first and second piezo elements are mounted to the end fittings a pre-selected distance from each other.
 14. The flow sensor sub-assembly according to claim 13, wherein said absorber sheath is one of heat shrunk onto at least a portion of said outside diameter of each of said flow tubes and adhered to at least a portion of each of said flow tubes with an adhesive.
 15. The flow sensor sub-assembly according to claim 13, wherein said first piezo element and said second piezo element are annular in shape and encircle the flow tubes at respective mounting points.
 16. The flow sensor sub-assembly according to claim 11, wherein each of said flow tubes is a stainless steel material.
 17. The flow sensor sub-assembly according to claim 11, wherein said absorber sheath is one of a plastic material and a PVC material.
 18. The flow sensor sub-assembly according to claim 11, further comprising a flow sensor base, wherein said flow sensor sub-assembly is contained within a flow sensor housing, wherein said flow sensor housing is coupled to the flow sensor base which contains a microprocessor and a circuit for providing an electrical signal from said flow sensor sub-assembly to said microprocessor within said flow sensor base, wherein said flow sensor sub-assembly is disposed after said flow sensor sub-assembly is used to sense a flow of at least one fluidic medicament, and wherein the flow sensor base is used with a different flow sensor sub-assembly. 